Various pick-up box covers have been proposed in the past. These include the covers described in the following:
Klanke U.S. Pat. No. 3,489,456 describes a two part rigid cap. The front part of the cap is permanently mounted on the front half of the truck box, while the rear half opens like a pivoted trunk lid in a passenger automobile. This system does not provide easy access to the full box and it limits the size of objects to be carried to those that can fit under the cap.
Boismier U.S. Pat. No. 3,768,858 describes a multi-panel cover. Two panels are carried on each side of the box and fold over into the centre to close the cover. In the open position, the stacked panels extend along the outsides of the truck box. The individual panels in this system are manipulated into position by hand, making opening and closing a complex operation. The presence of a joint at the centre of the cover leads to the possibility of rain or snow leakage into the cargo space. In the open position, the width of the truck is increased, which can be unacceptable in many cases.
Logue U.S. Pat. No. 3,833,255 describes a two panel cover for dump truck boxes. One of the panels is hinged to the front of the box and is pivoted by two hydraulic cylinders from the closed position to an open, horizontal position extending over the front of the truck. In movement, the front panel drags the rear panel across the top of the box. This arrangement consumes excessive amounts of power, scrapes the top of the box and may have difficulty in closing due to binding of the rear panel against the top of the box in the vertical position.
Fredin U.S. Pat. No. 4,140,339 describes a cover that extends over one side and half the top of a truck box. The cover is not a rigid construction but a tarpaulin or the like. This arrangement is unsuited for use with pick up truck boxes.
Steinberg U.S. Pat. No. 4,585,266 describes a cover for a maneure spreader in which two side by side panels are pivoted upwardly to one side of the spreader by an hydraulic cylinder joining the two. The weight of the unit is carried by a pin running in a track. This will cause problems if there is a build up of snow, ice or dirt in the track. In addition, the use of external hydraulic cylinders is not aesthetically acceptable in the modern pick-up truck market. A further problem with this cover if used with a pick-up truck box would be the tendency of rain or snow on the moving panel to run off into the box during opening.
The present invention proposes an alternative form of rigid truck box cover.